In this article
- What is nuchal translucency?
- The exam: when to do it, outcomes and costs
What is nuchal translucency?
Nuchal translucency (NT) is a prenatal screening test that consists of ultrasound measurement of a physiological collection of liquid present in the region of the nape of the fetus, between the skin of the nape and the occipital bone of the skull, where the vertebral column begins.
What is it for
This collection increases between the eleventh and thirteenth week of pregnancy in most fetuses affected by genetic diseases or some malformations. Its measurement in this gestational period allows you to calculate individual risk that a woman runs, compared to other expectant mothers of her own age to have a baby with a birth defect or a chromosomal abnormality such as
- la Turner syndrome,
- trisomy 21 (down syndrome),
- trisomy 18 (Edwards syndrome)
- or trisomy 13 (Patau syndrome).
Nuchal translucency is therefore considered as the most important marker for the prediction of fetal abnormalities and is one of the two tests that make up the bi-test or combined test. Undergoing it can be annoying, but not painful.
The exam: when to do it, outcomes and costs
When to do it
The ultrasound measurement of translucency can be performed at any time during pregnancy, even if the best time to identify any abnormalities in the baby is between the eleventh and the beginning of the fourteenth week of gestation. Normally the exam takes about 30-45 minutes to allow measurement of the fetus in indeterminate positions.
The advice of the experts is to contact specialized centers. The website of the Del Paesena Society of Obstetric and Gynecological Ultrasound and Biophysical Methodologies (www.sieog.com) provides online the list of certified facilities.
In order to undergo this screening test, the cranio-caudal length of the fetus (CRL) must be between 45mm and 84mm.
The value of the nuchal translucency in fact varies according to this length and it is therefore impossible to establish finite parameters that determine a situation of normality. The outcome of the examination must therefore be evaluated on the basis of particular curves that take this ratio into account.
Measurements exceeding 3,5 millimeters are normally considered to be at risk ("increased translucency"). However, even lower values could indicate risk factors.
Obstetric ultrasound with nuchal translucency - together with maternal blood sampling for the measurement of placental markers - is part of the combined test procedure, which has been included in the New Essential Levels of Assistance, as a pregnancy test passed by the National Health Service to all women. So it is free.
If you want to perform the test privately, the cost varies between 100 and 300 euros.
Questions and answers
Is the nuchal translucency test painful?
The test lasts 30-45 minutes and can be considered annoying, but it is not painful.
Is the nuchal translucency test dangerous?
As it is not an invasive examination, ultrasound measurement of nuchal translucency does not foresee any danger to the health of the fetus or mother.
Nuchal translucency examination: how is it performed?
The examination consists of an ultrasound that measures the thickness of a collection of fluid placed under the fetal neck in order to establish the likelihood of risk that the fetus will develop chromosomal abnormalities.
- test at screening
- dictionary of pregnancy